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Custom ASP.NET Datagrid Paging With Exact Count
- Introduction
- Accessing our Data
- The HTML Portion
- The Source Code
Introduction
Anybody in the DB world knows what paging database results is and its effect.
From the time I had started getting into good old classic ASP, I was intrigued
with the ability to divide large sets of data into sections of x records per
page. One thing that I didn't like about paging is that it seemed sites incorporated
just a < Prev and Next > link on the search results page. I wasn't satisfied
with such a lackluster paging technique, and from there I searched high and
low on every ASP Web site I could find to see if there was code to show more
advanced
paging options, such as how many pages were remaining to be paged through,
or, if the next page was the last page of results, how many records were on
that
last page. Unfortunately, I couldn't find any such code, so I had set out to
do it myself. (To see the proposed paging enhancements I like, check out the live demo for this article...)
I have since coded a number of techniques for advanced paging in classic ASP, but my latest challenge has been to incorporate the same paging techniques in ASP.NET! (For more information on ASP.NET, be sure to visit the ASP.NET Article Index.) Pssst, don't ask me to talk about redoing my app in Beta 1, and upon upgrading to Beta 2 was horrified that my code needed to be redone.... by the way, the code in this article is all Beta 2 compliant.
Now, if anyone has looked into the Microsoft .NET SDK and Quickstart samples you will find custom paging samples, but it's the usual next and prev stuff. Now let's see how we can kick this paging up a notch and tell us more detail about our data output.
This article was originally published on 4guysfromrolla.com.
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Hi, thanks, I appreciate your compliments.
I have written another older article that I think should help. It's entitled- Drilldown Datagrid Searching with ASP.NET.
This article demonstrates how to do a standard search, display the results in a datagrid, then further filter and search the datagrid itself and drilldown into the datagrid results themselves.
So to merge the two, work off of the aforementioned article and incorporate the custom paging. All this should be no problem, and plenty to get you up and running.
Also, for scalability purposes, read another article of mine here on DF - .NET Data Caching . Between the two you'll be able to provide some great functionality and performance.
I hope this helps!
- Jimmy Markatos
I loved your article on custom paging but would very much like to know how to apply it when you filter your initial data set to retreive specific records. I have a grid with 813 records sorted by user name. I have a search box in which a user can enter a name in order to filter the original dataset. If the search result in only 4 pages of records how can I page through that new set of records? Thanks in advance for any help and for the great article.
Check this site...
I too was on the same quest and I've created a best practices reference site that covers many enterprise topics necessary to create large scale enterprise sites.
Tankete, I just have try what you are asking for a couple of days ago :
The principe is simple : returning only a needed page from 50th to 60th records consists in querying this way :
SELECT * TOP 60 ... WHERE NOT IN SELECT TOP 50 * WHERE [joining primarykeys]
I have taken advices from Dino Esposito's MSDN articles, and have created a PageQuery function thats returns such a SQL statement, based on a normal SQL statement, primaryKey information, currentpageindex and pagesize.
This sample of code uses a custompaged enabled datagrid called dg, with a access database that contains a "HugeTable" table with a "ID" primary key.
Do not forget to enable custompaging to your datagrid
Private _Cx As OleDbConnection
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
_Cx = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;Password="""";User ID=Admin;Data Source=C:\Inetpub\wwwroot\labo\app\db\paged_datagrid.mdb;Mode=Share Deny None;")
If Not IsPostBack Then
dg.DataBind()
DataList1.DataBind()
End If
End Sub
'
Private Sub dg_DataBinding(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles dg.DataBinding
Dim sqlstr As String = PageQuery("SELECT * FROM HugeTable ORDER BY ID", "ID", dg.CurrentPageIndex, dg.PageSize)
_Cx.Open()
dg.VirtualItemCount = New OleDbCommand("SELECT COUNT(*) FROM HugeTable", _Cx).ExecuteScalar
Dim dr As OleDbDataReader = New OleDbCommand(sqlstr, _Cx).ExecuteReader(CommandBehavior.CloseConnection)
dg.DataSource = dr
End Sub
'
'
Private Function PageQuery(ByVal commandText As String, _
ByVal primaryKey As String, _
ByVal currentPageIndex As Integer, _
ByVal pageSize As Integer) As String
Dim SubQuery1_TopCount As Integer = IIf(currentPageIndex = 0, _
pageSize, _
currentPageIndex * pageSize + pageSize)
Dim SubQuery1 As String = Replace(commandText, _
"SELECT ", _
String.Format("SELECT TOP {0} ", SubQuery1_TopCount))
If currentPageIndex = 0 Then Return SubQuery1
SubQuery1 = String.Format("({0}) AS T1", SubQuery1)
Dim SubQuery2_TopCount As Integer = currentPageIndex * pageSize
Dim SubQuery2 As String = Replace(commandText, _
"SELECT ", _
String.Format("SELECT TOP {0} ", SubQuery2_TopCount))
SubQuery2 = String.Format("({0}) AS T2", SubQuery2)
Dim MainQuery As String = String.Format("SELECT t1.* FROM {0} LEFT JOIN {1} ON T1.{2}= T2.{2} WHERE T2.{2} IS NULL", _
SubQuery1, _
SubQuery2, _
primaryKey)
Return MainQuery
End Function
'
Private Sub dg_PageIndexChanged(ByVal source As System.Object, ByVal e As System.Web.UI.WebControls.DataGridPageChangedEventArgs) Handles dg.PageIndexChanged
dg.CurrentPageIndex = e.NewPageIndex
dg.DataBind()
End Sub
Hope it helps. For SQL server, the built query could be better implemented using subqueries instead of inner join, which is much more faster in access.
Laurent.
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